JPS6077350A - Sealing material for alkaline battery - Google Patents

Abstract

PURPOSE:To obtain an alkali-proof sealing material having a great sealing effect against external load by adding a styrene-butadiene block copolymer to blown asphalt. CONSTITUTION:After a battery lid 3 is attached to a battery container 1, a sealing material 6 is packed between the container 1 and the lid 3 to bind them together by sealing. Either a mixture prepared by combining blown asphalt with a styrene-budadiene block copolymer having a higher softening point than blown asphalt or a mixture prepared by adding a wax to the above mixture is used as the sealing material 6. The styrene-budadiene block copolymer works as a hot- melt-type adhesive. Therefore the ductility of the sealing material 6 increases and an increased resistance to texternal load is achieved as the percentage of the copolymer in the sealing material increases. However, in order to avoid difficulty in sealing resulting from increased viscosity of the sealing material 6 caused when it is molten at around 180 deg.C, the proper proportion of the copolymer is 5-35wt% of the sealing material 6. Addition of a wax increases the compatibility between the above adhesive and blown asphalt and is specially advantageous when a increased amount of the adhesive is used.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a sealing material for alkaline batteries, and in particular, in an air battery using a resin battery case and a battery cover, the present invention relates to a sealing material for an alkaline battery, and in particular, in an air battery using a resin battery case and a battery case lid, the present invention relates to a sealing material for an activated carbon anode to the battery case lid. This invention relates to fixing the seal and improving the pitch-based sealing material used to seal the battery case and the battery case lid.

Conventional Structure and Problems Pitch, which has a softening point of about 80° C., is generally used as a sealing material for air batteries because it is inexpensive.

However, when using only the pitch, the adhesion with the resin etc. is weakened, and external forces such as impacts may cause damage.
There is an inconvenience that cracks may occur.

In addition, when using pitch with a low softening point to strengthen adhesion and prevent cracking, if the environmental temperature is 30 to 40°C, the pitch may soften and sag during use of the battery. , the sole could become incomplete. In order to improve this, attempts have been made to mix in a small amount of oil such as soybean oil, but during use the soybean oil is saponified by alkali and becomes brittle and may peel off due to external impact. .

However, when mixed with wax or the like, it still has alkali resistance, and its adhesion and impact resistance are considerably improved. However, if a low-rigidity resin such as polypropylene is used for the battery case, if the resin is deformed due to the way the battery is fixed during use or due to external impact, the pitch elongation will be small.
Peeling from the resin may occur.

Purpose of the Invention The present invention aims to improve the above-mentioned drawbacks of pinch-type sealing materials, and is an improved sealing material that is resistant to alkali, has a softening point higher than conventional pitch, and has a high elongation at room temperature. The purpose of the present invention is to provide a seal that has a large sealing effect even against external loads.

Structure of the Invention The present invention is a sealing material made by adding a styrene-butadiene block copolymer having a higher softening point or wax to bromine asphalt, which is represented by pitch, to improve its elongation and adhesion. be.

Description of examples An example applied to the air battery shown in the figure will be described.

Reference numeral 1 denotes a battery case made of polypropylene, which houses a zinc cathode 2. 3 is a polypropylene battery case lid, into which a waterproof activated carbon anode 4 is inserted, a sealing material 5 is melted and filled, and after cooling, the battery case lid 3 is fitted into the battery case 1. Then, a date seal 6 is filled between the battery case and the battery case lid to seal and fix. After that, the caustic potassium electrolyte 7 is injected. 8 is Cal/Rum hydroxide particles as an electrolyte regenerant. 9 is an anode cover molded integrally with the battery case lid, and there is a ventilation hole 10 on the side.
has.

Next, a compounding example of the sealing material will be explained. The physical properties of the styrene-butane block copolymer are shown in Table 1. It's ox.
The raw materials of brominated asphalt-based pitch and microcrystalline wax are shown in Tables 2 and 3, respectively.

Note that the penetration rate is the penetration of a needle with a load of 1002 in 5 seconds.

Table 1 Softening point 110℃ Melt viscosity (160℃) 560oCP Elongation (25℃) 20cm Table 2 Softening point 80℃ Needle strength (25℃) 2-3mm Elongation (25℃) 2 on 3rd Surface melting point 80~85℃ Needle temperature (25℃) 17~20wn Oil content 2.5% or less The above pitch and block copolymer in a weight ratio of 85:15
Table 4 shows the physical properties of sealing material A, which is a mixture of pitch, block copolymer, and wax in a weight ratio of 70:15:15.

Table 4 Styrene-butadiene Bronok copolymer acts as a hot-melt adhesive, and as its addition ratio increases, the elongation of the sealing material increases and its resistance to external loads increases.

However, when dissolved at about 180°C, the viscosity becomes high, making sealing difficult. Unfortunately, this adhesive has a higher shrinkage rate than pitch, so it causes a large sink when left to cool, and if the proportion of the adhesive added is too high, the center of the seal will sink after being left to cool, resulting in an incomplete seal. Therefore, the appropriate proportion of this adhesive added is 5 to 35% by weight. Furthermore, wax has the effect of increasing the compatibility between the above-mentioned adhesive and bromine asphalt, and is particularly advantageous when the amount of adhesive is increased. The appropriate proportion of wax to be added is 6 to 15% by weight; if it is more than this, sink marks will become large.

As is clear from the above comparison of physical properties, the sealing material according to the present invention has better elongation than bromine asphalt.

Regarding alkali resistance, the battery shown in the figure was manufactured and compared with a case using bromine asphalt, but no difference was observed in the leakage resistance for about 2 years with alkali, which tends to leak. However, when the battery shown in the figure was manufactured and a load was applied to the anode cover 9, the load at the groove where the sealing material 5 peeled off from the anode 4 was measured. 9, but for batteries using brome asphalt it was 25! Met.

Effects of the Invention As described above, the sealing material of the present invention has excellent alkali resistance and is particularly resistant to external loads, so it has great utility as a sealing material for air batteries that are subject to vibration and shock.

[Brief explanation of drawings]

The figure is a longitudinal sectional view of an air cell used in an example of the present invention. 1...Battery container, 2...Cathode, 3--Battery container lid, 4-
...Anode, 5,6...- Sealing material.

Claims (2)

[Claims] (1) A sealing material for alkaline batteries containing a mixture of 6 to 35% by weight of bromine asphalt nystyrene-phthalene pronk copolymer. (2) Apply 6 to 15 layers of wax to brome asphalt.
%, styrene-butadiene polymer copolymer from 6 to 35
Sealing materials for alkaline batteries each added in weight percent.